Telephone-exchange system



W.- T. POWELL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED FEB. 6. 1919.

Patented Jan. 4, 1921..

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wmrann T. rowELL/or ROCHESTER, NEW YORK, ASSIGNOR To wEsTRRN ELRoTR rccommny, INCORPORATED, or new YORK, N. Y., A CORPORATION or NEW roan.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Jan. 4, 1921.

Application filed February-6, 1919. Serial No. 275,842.

To all whomit may concern:

Be it known that I, WINFRED T. POWELL, a citizen of the United States, residing at Rochester, in the county of Monroe, State of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to machine switching telephonesystems, and particularly to systems'wherein special character service 1s provided.

The object of the invention is to provide means whereby a toll operator, upon answering the call of a subscriber whose line has been automatically extended to her POSltlOIl, may expeditiously identify such calling l1ne.

Heretofore such an object has been accomplished through the use of a large amount of complicated apparatus or through the use of a complete subscribers multiple before the toll operator, whereby she might identify the calling line by making a revertive busy test.

The presentinvention is an improvement over such arrangements in thata calling line may be identified through a revertive busy test of the calling line made over an arrangement of apparatus, an organization of circuits employing a number of testing points which is an extremely small percent.- age of the complete subsoribers multiple.

A feature of the invention is a plural bank of testing points connected to groups of subscribers lines in such a manner that any one of a large number of such lines may be tested by making connections separately to one testing point on each of the said banks. This and other features will appear in the following description and appended claims.

In the drawing a subscribers substation is represented at the left-hand upper corner connected to aline switch with an indicated extension to a toll operators position at the right-hand side of the drawing. In the lower portion of the left-hand side, the grouping arrangement of the calling lines is indicated and on the right-hand lower side the two groups of testing points are shown.

In general, the operation of this system is as follows: 1

The subscriber at station 1, by removing his receiver from. its hook, causes the line switch 2 to pick an idle trunk to a numerical switch 3, WhlCh he thereupon directively actuates to extend his line to a toll operators position, this invention being peculiarly adapted for use in connection with toll and long-distance traffic. of the subscribers line'to the toll operators position, a signal lamp'a'is caused to glow, whereupon the operator makes connection to the selected trunk associated with the signal 4 and receives the instructions subscriber. In order to verify the number of the calling substation, the toll'operator tests first a point in the bank of testing points 5 and then a point in the bank of the testing points 6', both of which points are associated with the calling line. If she receives the revertive busy test upon each point which she tests she knows that he has given the number correctly and she there- Upon the extension of the calling upon proceeds to set up the connection in any ordinary and well-known manner.

is established .from ground, the upper inner,

armature and back contact of cut-off relay 7, to and through the apparatus of the sub station 1, the innermost lower armature and back contact of cut-ofi' relay 7 the winding of line relay 8 to battery andground. The line relay 8 is energized and attracts its armature. A circuit is thereupon established for the stepping magnet 9 of the line switch 2'extending from ground, the Winding of magnet 9, brush 10, the normal terminal upon whichit rests, the armature and contact of line relay 8, the armature and contact of magnet 9, through a resistance 12 to battery and ground. Magnet 9 by including in its circuit its own armature and contact is self-interrupting. Upon the first actuation of magnet 9, the brush 10 is stepped oif of its normal contact and its circuit is removed from the control of the line relay, now extending from ground, the winding of magnet 9, the brush 10, the contacts over which it travels, the back contact and lowermost armature of cut-ofi' relay 7, the armature and contact of magnet 9, resistance 12 .to battery and ground. Each time that magnet 9 attracts its armtaures to cause the stepcuit and therefore causes the continuous stepping of such brushes until they are stopped by the finding ofan idle line. Such idle lines are indicated by the presence of ground on the third from the bottom row of contacts.

We will assume that'the last set of contacts is the first one leading to an idle line.- Therefore, when this set of contacts is reacheda circuit is established from ground, the contact and armature of relay 13, brush 14, lower contact of the middle lower armature of relay 7, armature and contact of relay 8, armature and contact of magnet 9, resistance 12 to through the battery and ground. In this manner and rent delivered to magnet 9 when it retracts its armature after placing the brushes on the last set of contacts, is so reduced that it cannot a ain be energized. At the same time, cut-o relay 7 attracts its armatures, and through the movement of its lowermost armature, insures the non operation of magnet 9 by opening its circuit. Through I the operation of the cut-off relay 7, the. subscribers line is cut off from the line relay and extended through the brushes 15 and 16 to the selected idle line. At the uppermost armature of cut-off relay 7, a circuit is closed from battery and ground, through the winding of relay 13, the brush 17, the

uppermost armature and contact of cut-ofl' relay 7 the upper winding of cut-oft relay 7, conductor 29, the primary winding of induction coil 18, to ground. Relay 13 becomes energized and opens the circuit for the lower winding of cut-off relay 7. Cut-off relay 7, however, retains its armatures in their actuated position, due to the energization of'its upper winding.

The idle line selected by the line switch extends to a numerical switch of any wellknown type, which may be actuated through the manipulation of a substation sending device indicated by 19. Only the parts of its circuits which form a part of the present invention are shown.

We will assume that the subscriber at sub: station 1 manipulates his sending device 19 to set the brushes of the numerical switch 3 on to the terminals of a line leading to a recording toll operators position. WVhen switch 3 has thus been properly set, a circuit is established from grounded battery, winding of relay 20, inner left-hand armature and contact of relay 11, the lower talking strand of the connection through the windings of polarized relay 23, the windings 50 and 51 of the repeating coil, the upper strand of the talking connection, the outer lefthand armature and contact of relay 11 to round. Relay 20 becomes energized in this circuit and attracts its armature whereby a agency of resistance 12, the curcircuit is established for the lamp signal 4. The operator noticing the glowing .of the lamp 4 inserts the plug 25 into the jack 26 circuit and through its right-hand armature and contact locks up to the ground on the third conductor leadin back through the winding of cut-off relay 7, normal \upper winding of cut-o relay 7 to ground at by current fiowingin this direction. How

ever, after the operator inserts the plug 25 into the jack 26,"she actuates her listening key 28 tocommunicate with the calling subscriber at substation 1. This establishes a potential circuit for the reversal of current in the line between the. numerical switch and the operators position whereby the relay 23 is energized at the proper time as will hereinafter be more fully described.

Upon receiving the instructions of-the subscriber at substation 1 the operator requests that his line number be given her. Assuming that the substation 1 is actually numbered 2244 and that he gives this number cor- -rectly to the operator, she may check it in the following manner.

First, however, it will be well to explain that the subscribers lines, assuming this to be a ten-thousand line exchange, are divided into groups of one hundred lines each, there being one hundred of such groups. A conductor such as 29 is multipled at the proper point to the upper winding of cut-off relay 7 of every subscribers line, the last two digits of whose number are 44. In like manner, the conductor 30 will be multipled at the proper points to the cut-off relays of those lines whose last two digits are 45, and the conductor 31 to the lines whose last two digits are 46. In this manner every line in a ten-thousand exchange is connected to some one of the testing points in the bank of testing points 6.

A conductor32 is multipled to the lower middle armature of the cut-off relay 7 of each of those subscribers lines, the first two digits of which are 22. In like manner the the testing oints the bank of testing points 5. ence, throu h the testing of two oints, one in the bank 5 and one in the ank 6, any particular line may be checked twice.

Asto the manner in which this is done, the following description will sutlice.

We have assumed that the calling substation 1 is numbered 2244. The operator therefor touches the tip of her plug 35 to the testing point 22 in the bank 5. Since this testin point is connected by induction coil 52 ant? the conductor 32, to the winding of cut-ofi' relay 7 individual to the calling line 2244, a revertive busy test will be established. Ground at the induction coil 52 will be extended through the testing point 22, the tip of the plug 35, the upper armature and back contact of relay 36, the winding of relay 37, to battery and ground. Relay 37 is energized in this circuit and through its outer armature extends ground through the outer right-hand contacts of listening key 28 to the winding of relay 38, battery and ground.- Relay 38 in turn becomes energized and through the action of its armatures reverses the direction of the flow of current through the polarized relay 23 which becomes energized. Through the inner armature of relayv 37 a revertive busy tone from the source BZ is connected through the outer left-hand contacts of listening key 28 to the sleeve of the plug 25, the sleeve of the jack 26, the right-hand armature and contact of relay 11, the brush 17 of the line switch 2, the uppermost armature and contact of cut-ofi' relay 7 the upper winding of cut-off relay 7, the primary winding of induction coil 18 to ground. Through the actuation of polarized relay 23 a ground is placed upon the conductor leading to brush 14 during the actuation of relay 37,. thence through the lower winding of cut-oil relay 7, conductor 32, to the primary winding of induction coil 52, to ground. The revertive busy tone current flowing through the upper winding of cutoff relay 7 is induced into the lower winding through the closure of the circuit just described and'such busy tone is projected over the conductor 32, to the induction coil 52, and then into agency to the testing point 22. From there it travels through the tip of the plug 35, the upper armature and back contact of relay 36, the conductor 39, the condenser 40, the operators receiver 41, the

winding 42 of the operators induction coil,

the inner right-hand contacts of the listening key 28, to the ground 43. Thus the operator is notified that she is testing the point associated with the calling line.

If the calling line, however, had actually been numbered 2144, the polarized relay 23 would have been energized in the same manner through this test, but the busy tone would j not have been connected to theconductor 3 3 and communicated to the testing pomt 21. Hence the operator in testing the point 22 would have received norevertive bus tone,

he operator now has knowledge of the fact that the first two digits of the calling line had at least been given correctly. In order to" determine if the last twohad been given correctly she tests the point 44 iii the 'bank 6. In the manner described, the revertive busy tone is transmitted through the upper winding of the cut-off relay 7 connected with the calling subscribers line to the primary winding of the induction coil 18. By testing the point 44 the revertive busy tone is induced in a circuit including ground, the secondary winding of the induction coil '18, the testing point 44, the tip of the plug 35 and thence over the circuit including the operators receiver hereinbefore and would have known that the number had been given incorrectly.

- A further check may be made by the operator in the following manner:

It is possible that another operator might be'making a revertive busy test on a line, say No. 3744, in which case a busy tone would be induced into the induction coil 18, as hereinbefore described, and transmitted to the testing point 44 and this operator would have received: it. If, however, she taps the testing point 44 with the tip of her plug 35 in a manner peculiarly her own, she may be sure that the revertive busy tone which she is receiving is that propagated by her own cord circuit. If she leaves the tip of the plug 35 on'the-testing point 44 for a short interval and the other operator makes a similar test by rapidly tapping the tip of her plug 35 on the testing point associated with the thirty-seventh hundred, in the back 5, this operator will hear the other operators code and know that the busy test which she is receiving is not propagated by her own cord circuit.

. After these operations have been completed the toll operator may instruct the calling subscriber to hang up so that she may recall him when she had established the toll connection or give him any other instructions which the traific rules prescribe. When the calling subscriber hangs up and the operator removes the plug 25 from the jack 26, the connection is disestablished in any well-known manner which will not be described here since it forms no part of the present invention.. 4

What is claimed is:

1. In a testing system, circuits, testing points, each said testing point being associated with a different plurality of said circuits and each said circuit being associated with a different plurality of testing points, a source of busy tone with one of said circuits, and means for testing for said busy tone on said testing points associated wit said circuit.

2. In a testing system, circuits, testing points, an induction coil associated with each testing point, each said induction coil being associated with a different plurality of said circuits and each said circuit being associated with a different plurality of said induction coils, a source of busy tone, means for associating said busy tone with one of said circuits, and means for testing for said busy tone on said testing points associated with said circuit.

3. In a testing system, circuits, a relay individual to each srid circuit, a winding on said relay for its initial actuation, a second winding .on said relay for its subsequent actuation, a testing point associated with said second winding, a testing point associated with said first winding upon the actuation of said relay, a source of tone, means responsive to thetesting of any of said testing points for connecting said source of tone to said second winding, means responsive to the testing of said testing point associated ducin thereb a si nal. 4.1% y a with said tecondwinding for rendering said tone audible and producing thereby a signal, and means responsive-to the testing'of said testing point associated with said first winding for inducing therein currents similar to those propagated by said source of tone which is connected to said second winding for rendering said tone audible and proa testing system, circuits, a relay individual to each said circuit, a winding on said relay for its initial actuation, a second winding on said relay for its subsequent actuation, an induction coil connected to said second winding, an induction coil connected to said first winding upon the actuation of said relay, a testing point associated with each said" induction coil, a source of tone means responsive to the testing of any of said testing points for connecting said source of tone to said second windingg means responsive to the testing of said testing point associated with said' second winding for rendering said tone audible and producing thereby a signal, and means responsive to the testing of .said testing point associated with said first winding for inducing therein currents similar to those propagated by said source of tone which is connected to said second winding for rendering said tone audible and producing thereb a signal.

In witness whereo I hereunto subscribe my name this 27th day of January, A. D 1919.

WINFRED T. POWELL. 

